TW201943647A - 6H-type hexagonal barium germanium oxide, manufacture thereof, sintered body thereof, and target made of same - Google Patents

Abstract

Provided are barium germanium oxide having a band gap of 3 - 4 eV, a manufacturing method of the barium germanium oxide, a sintered body of the barium germanium oxide, and a target made of the sintered body. The barium germanium oxide of the present invention includes at least Ba, Ge, and O, and a crystal represented by a general formula of ABO3(Here, A includes at least Ba, and B includes at least Ge.), which has a 6H hexagonal perovskite structure.

Description

Hexagonal 6H-type barium germanium oxide, manufacturing method thereof, sintered body, and target material

The present invention relates to a barium germanium oxide, a method for manufacturing the same, a sintered body, and a target, and in particular, it relates to a hexagonal 6H type barium germanium oxide, a method for manufacturing the same, a sintered body, and a target.

Transparent displays are being used for displays of portable information terminals such as smart phones and tablets. The currently used transparent conductive materials are based on rare metals such as indium oxide, so it is necessary to explore alternative materials in terms of resources. For example, Ba (barium) or Si (silicon), or Ge (germanium) of the same family as Si are abundant in resources, and it is ideal to develop materials using these elements.

An oxide represented by BaSiO ₃ having a cubic crystal system, a rhombohedral symmetry 9R type, and a hexagonal 6H type perovskite structure has been developed (for example, refer to Non-Patent Documents 1 and 2). According to Non-Patent Document 1, cubic crystalline BaSiO ₃ can be obtained. However, it is amorphous at atmospheric pressure and cannot be used as a transparent conductive material. According to Non-Patent Document 2, 9R-type and 6H-type BaSiO ₃ can be obtained. However, both of them become amorphous at atmospheric pressure, so they cannot be used.

Furthermore, an oxide represented by BaGeO ₃ having a hexagonal 9H type and a hexagonal 4H type perovskite structure has been developed (for example, refer to Non-Patent Document 3). 9H-type _3-based BaGeO BaGeO by limestone structures having a ₃ silicon prosthesis in a temperature range of 650 ℃ ~ 850 ℃, 9.5 GPa ~ 12 GPa range of processing and synthesis. Similarly, 4H-based type BaGeO ₃ BaGeO by limestone structures having silicon at 950 ℃ ~ fake temperature in the range of ₃ 1400 ℃, 9.5 GPa ~ 12 GPa range of processing and synthesis. However, no report has been made on such band gaps. In addition, although BaGeO ₃ of the orthorhombic system can be obtained under normal pressure, its band gap is as large as 5.7 eV, and therefore it is considered that it cannot be used for transparent conductive materials.
[Prior technical literature]
[Non-patent literature]

[Non-Patent Document 1] H. Hiramatsu et al., Inorg. Chem., 56, 10535-10542, 2017
[Non-Patent Document 2] H. Yusa et al., Am. Mineral., 92, 648-654, 2007
[Non-Patent Document 3] Y. Shimizu et al., High-Temperature-High Pressures, 2, 113–120, 1970

[Problems to be solved by the invention]

Based on the foregoing, it is a problem of the present invention to provide a barium germanium oxide having a band gap of 4 eV or less, a method for producing the same, a sintered body, and a target.
[Technical means to solve the problem]

The barium germanium oxide of the present invention may contain at least Ba (barium), Ge (germanium), and O (oxygen), and crystals represented by the general formula ABO ₃ (where A contains at least Ba and B contains Ge at least). The crystal represented by ABO ₃ has a hexagonal 6H type perovskite structure. With this, the above problems can be solved.
The above-mentioned crystal represented by ABO ₃ may have the symmetry of the space group P6 ₃ / mmc, and the lattice constants a, b, and c respectively satisfy the following ranges:
a = 0.56006 ± 0.05 (nm)
b = 0.56006 ± 0.05 (nm)
c = 1.3653 ± 0.1 (nm).
The barium germanium oxide of the present invention may have a band gap in a range of 2.5 eV or more and 4 eV or less.
The barium germanium oxide of the present invention may have a band gap in a range of 2.5 eV or more and 3.5 eV or less.
The A may further contain a material selected from La (lanthanum), Ce (cerium), Pr ()), Nd (neodymium), Sm (钐), Eu (铕), Gd (釓), Tb (鋱), Dy (镝), Ho ('), Er (铒), Tm (銩), Yb (镱), Lu (镏), Y (yttrium), Sc (钪), and In (indium).
The A may further contain the selected element in a range of 0.05 mol% or more and 15 mol% or less.
The B may further contain Si.
The method for producing barium germanium oxide according to the present invention may include the following steps: a raw material powder containing at least barium germanium oxide represented by BaGeO ₃ having an orthorhombic crystal in a temperature range of 900 ° C. to 2300 ° C., 7.5 It is processed in a pressure range above GPa and below 45 GPa. With this, the above problems can be solved.
The above-mentioned processing step may be performed by a high-temperature and high-pressure treatment method or an impact compression method using at least one device selected from the group consisting of a diamond anvil device, a multiple anvil device, and a belt-type high-voltage device.
The above-mentioned processing steps can be performed by a high-temperature and high-pressure processing method using a diamond anvil device or a multiple anvil device. The above-mentioned pressure range is in a range of 12 GPa to 44 GPa before processing, and 7.5 GPa or more after processing. And in the range of 40 GPa or less. The above-mentioned pressure range may be in a range of 12 GPa or more and 24 GPa or less before processing, and a range of 8.0 GPa or more and 18.5 GPa or less after processing. The temperature range may be in a range of 1200 ° C or higher and 2000 ° C or lower.
The above temperature range may be in a range of 1300 ° C to 1500 ° C, the above pressure range may be in a range of 19.5 GPa to 24 GPa before treatment, and 12.5 GPa to 16.5 GPa after treatment.
The raw material powder may be a powder having a particle diameter of 100 nm to 500 μm.
The processing step described above allows the raw material powder to react for a period of 5 minutes to 24 hours.
The raw material powder may further contain a material selected from the group consisting of Y, Sc, In, Si, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Substance of at least 1 element.
The present invention may be a sintered body comprising the barium germanium oxide as described above. Such a sintered body can solve the problems as described above.
The present invention may be a target for physical vapor deposition, which includes the sintered body as described above. With such a target, the above problems can be solved.
[Effect of the invention]

The above-mentioned barium germanium oxide may have a hexagonal 6H type perovskite structure. In this way, the symmetry of the crystal is reduced, and the band gap can be reduced below 4 eV. Such barium germanium oxide can be made into a transparent conductive substance by dopant or defect control.

The method for manufacturing barium germanium oxide as described above may include the following steps: a raw material powder containing barium germanium oxide represented by BaGeO ₃ having an orthorhombic crystal, at a temperature range of 900 ° C to 2300 ° C, 7.5 GPa The heat treatment is performed in a pressure range above 45 GPa. In this way, the crystal structure of the obtained product is not easily destroyed under one atmospheric pressure, and it can become a stable barium germanium oxide.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same elements are assigned the same reference numerals, and descriptions thereof are omitted.

In an embodiment of the present invention, a barium germanium oxide having a hexagonal 6H type perovskite structure and a method for manufacturing the same are described.

FIG. 1 is a schematic view showing a crystal structure of barium germanium oxide in an embodiment of the present invention.

In the embodiment of the present invention, the barium germanium oxide may contain at least Ba (barium), Ge (germanium), and O (oxygen), and may be represented by the general formula ABO ₃ (where the element A contains at least Ba and the element B contains at least Ge) Indicated. Furthermore, regarding the embodiment of the present invention, in the barium germanium oxide, the crystal represented by ABO ₃ may have a hexagonal 6H type perovskite structure. Furthermore, in the description of this case, the oxygen in "ABO ₃ " may include a state of excess oxygen or oxygen vacancies, which can be explained in this specification.

The inventors of the present case found a barium germanium oxide having a hexagonal system 6H type perovskite structure different from the existing crystal structure of barium germanium oxide. As a result, the symmetry of the crystal was successfully reduced. As a result, in the examples of the present invention, the band gap of the barium germanium oxide was found to be 4 eV or less.

Here, the 6H-type BaGeO ₃ synthesized by the present inventors is a crystal in which all the A elements are Ba and all the B elements are Ge in the above-mentioned crystal represented by ABO _3. According to the crystal structure analysis of the 6H-type BaGeO ₃ The 6H type BaGeO ₃ system belongs to the hexagonal crystal system and belongs to the P6 ₃ / mmc space group (Space Group 194 of International Talbes for Crystallography). Table 1 shows the crystal parameters and atomic coordinate positions. The 6H-type BaGeO ₃ having such a crystallization parameter is within a range known to the present inventors, and has not been reported before.

[Table 1]

In Table 1, the lattice constants a, b, and c represent the length of the axis of the unit lattice, and α, β, and γ represent the angles between the axes of the unit lattice. Atomic coordinates indicate the position of each atom in the unit lattice.

The following analytical results were obtained. In the crystal, each atom of Ba, Ge, and O is present, Ba is present at two kinds of sites (Ba1 to Ba2), and Ge is present at two kinds of sites (Ge1 to Ge2). O exists in two kinds of sites (O1-O2). As a result of analysis using the data in Table 1, it is known that 6H-type BaGeO ₃ has a structure shown in FIG. 1 and has a structure containing Ba in a tetrahedron formed by a bond between Ge and O.

As the crystal having the same crystal structure as the synthesized 6H-type BaGeO ₃ , there is a crystal represented by ABO ₃ as described above (the element A may contain, in addition to Ba, a member selected from La (lanthanum), Ce (cerium), Pr (鐠), Nd (neodymium), Sm (钐), Eu (铕), Gd (釓), Tb (鋱), Dy (镝), Ho ('), Er (铒), Tm (銩), Yb ( (Ii) at least one element in the group consisting of Lu (镏), Y (yttrium), Sc (钪), and In (indium. Element B may contain Si in addition to Ge). By containing such elements other than Ba and Ge, the lattice constant can be changed. Those crystal structures, the positions occupied by the atoms, and the atomic positions given by their coordinates are essentially unchanged, and can also be used as the barium germanium oxide in the embodiment of the present invention. Even if the lattice constant is changed, but the chemical bond between skeleton atoms does not change greatly, it can also be used as the barium germanium oxide in the embodiment of the present invention. In the embodiment of the present invention, the lattice constants obtained by performing Rietwald analysis on the space group of P6 ₃ / mmc from the results of X-ray diffraction or neutron diffraction of the target substance and The length of the chemical bond (distance between adjacent atoms) of Ge-O and Ge-Ba calculated from the atomic coordinates is ± 5% compared to the value calculated from the crystal lattice constants and atomic coordinates shown in Table 1. In the cases below, the same crystal structure can be determined. If the length of the chemical bond exceeds ± 5%, the chemical bond is broken and may become other crystals. As another simple determination method, the main peak of the X-ray diffraction of 6H-type BaGeO ₃ (for example, about 10 diffraction intensities) can be compared with the main peak of the target substance to substantially coincide, It was determined that the crystal structure was the same.

In particular, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, and In, which can be contained in the A element, can all function as dopants. These may allow carrier control, so in the embodiment of the present invention, it may be advantageous to use barium germanium oxide as a transparent conductive material. These dopants are dopants within a range that allows the crystalline structure to be maintained. For example, the doping amount may be in a range of 0.05 mol% to 15 mol%, and preferably in a range of 0.05 mol% to 10 mol%. For example, it may be 0.01 mol% or more or 0.05 mol% or more, and may be 15 mol% or less or 10 mol% or less.

Carrier doping can also be performed by oxygen vacancies. Thereby, it can function as a transparent conductor material. The vacancy amount may be in a range of 0.05% to 10%. Furthermore, the amount of vacancies can be measured by a thermal balance (TG) measurement in a dry oxygen atmosphere.

Furthermore, the crystal represented by ABO ₃ may have the symmetry of the space group P6 ₃ / mmc. In addition, the lattice constants a, b, and c preferably satisfy the following ranges:
a = 0.56006 ± 0.05 (nm)
b = 0.56006 ± 0.05 (nm)
c = 1.3653 ± 0.1 (nm).
Thereby, crystallization can become particularly stable. Also, the band gap can be reduced.

In an embodiment of the present invention, the barium germanium oxide may include a crystal represented by the above-mentioned ABO ₃ . In addition, it may have a band gap in a range of 2.5 eV or more and 4 eV or less. More specifically, in the embodiment of the present invention, the barium germanium oxide may have a band gap in a range of 2.5 eV or more and 3.5 eV or less when the element A is Ba and the element B is Ge. With such a band gap, in an embodiment of the present invention, barium germanium oxide can be used as a transparent conductive material. Furthermore, by adjusting the composition, it is possible to have a band gap in a range of 2.9 eV or more and 3.3 eV or less.

Next, in an embodiment of the present invention, an exemplary method for manufacturing barium germanium oxide will be described.
FIG. 2 is a diagram illustrating a process of manufacturing barium germanium oxide in an embodiment of the present invention.

In the embodiment of the present invention, a manufacturing method using a raw material powder containing at least a barium germanium oxide represented by BaGeO ₃ having an orthorhombic crystal as an raw material powder can be exemplified. Generally speaking, BaGeO ₃ with orthorhombic crystals is barium germanium oxide calcined at atmospheric pressure, which is an available barium germanium oxide. From this viewpoint, it is sometimes referred to as the normal-pressure phase BaGeO ₃ . The inventors of the present case have found that high-temperature and high-pressure treatment is performed by using raw material powders containing at least the atmospheric pressure phase BaGeO ₃ in a temperature range of 900 ° C. to 2300 ° C. and a pressure range of 7.5 GPa to 45 GPa (hereinafter referred to as simply Treatment) to produce the above-mentioned barium germanium oxide having a hexagonal 6H type perovskite structure. At a temperature of less than 900 ° C and a pressure of less than 7.5 GPa, it is easy to become a low-pressure barium germanium oxide. At a temperature higher than 2300 ° C and a pressure higher than 45 GPa, if the obtained barium germanium oxide is placed at an atmospheric pressure at normal temperature, it will easily become amorphous. In addition, in the present specification, the low-pressure type barium germanium oxide may mean a case where the structure includes an oxide of GeO ₄ as a tetracoordination. For example, a complex phase of BaGe ₂ O ₅ and Ba ₃ GeO ₄ may also be included in this oxide.

Here, the differences between the manufacturing method of the 4H-type BaGeO ₃ described in the aforementioned Non-Patent Document 3 and the manufacturing method in the embodiment of the present invention will be described. In Non-Patent Document 3, BaGeO ₃ having a pseudo wollastonite structure is used as a raw material. However, the present inventors and others use a normal-pressure phase BaGeO ₃ as a raw material, which is different in this respect. The inventors of the present case found that by using the atmospheric phase BaGeO ₃ and satisfying the above-mentioned conditions, the crystal structure of the product is not destroyed even at an atmospheric pressure at normal temperature. In this way, it was found that a barium germanium oxide having a hexagonal 6H type perovskite structure can be manufactured stably.

The raw material powder is preferably a powder having a particle diameter of 100 nm to 500 μm. This can further promote the reaction. A powder having a particle diameter of 200 nm to 200 μm is preferred. In addition, in this specification, a particle diameter is a volume-based median diameter (d50) measured by a Microtrac or laser scattering method.

The raw material powder may further contain at least one selected from the group consisting of Y, Sc, In, Si, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. 1 elemental substance. Thereby, a crystal represented by ABO ₃ can be obtained (the element A may contain, in addition to Ba, selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu At least one element in the group consisting of Y, Y, Sc, and In. The B element may further include Si in addition to Ge). In addition, the amount added may be within a range that can maintain the same crystal structure as the crystal structure shown in Table 1. For example, in the case of adding Si, a normal pressure phase BaSiO ₃ and / or Si metal may be used as the Si-containing substance.

A substance containing at least one element selected from the group consisting of Y, Sc, In, Si, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu These can be such simple metals, oxides, carbonates, and the like. Furthermore, in addition to these additive substances, germanium oxide powder may be added in order to adjust the composition.

The time for the high-temperature and high-pressure treatment varies depending on the amount of raw materials or the equipment used. For example, the time may be 5 minutes to 24 hours.

The above-mentioned processing steps can be performed, for example, by a high-temperature and high-pressure treatment method or an impact compression method using at least one device selected from the group consisting of a diamond anvil device, a multiple anvil device, and a belt-type high-pressure device. These methods can achieve the above-mentioned temperature range and pressure range. It is sufficient to use a device capable of achieving the above-mentioned high temperature and high pressure conditions. Furthermore, it is not necessary to be limited to the above-mentioned device.

Here, a case where processing is performed by a diamond anvil device in which a raw material powder is filled in a diamond anvil unit will be described.

FIG. 3 is a schematic view showing an entire diamond anvil device including a diamond anvil unit.
FIG. 4 is a schematic view showing details of the diamond anvil device of FIG. 3.

As the diamond anvil device, an existing one can be used. As shown in FIG. 3, the ground diamond is polished so that the bottom surface becomes flat so that the bottom surface faces the surface, and pressure is applied to the bottom surface. As shown in FIG. 4, a raw powder containing BaGeO ₃ at a normal pressure phase is held by a pad and diamond.

Then, the above-mentioned pressure is applied to the diamond anvil device, and a laser beam such as an optical fiber laser may be irradiated to the raw material powder. The heating temperature can be judged by the color temperature, and the laser irradiation time can be several minutes to tens of minutes after the temperature becomes constant.

In the case where the above-mentioned treatment is performed by the high-temperature and high-pressure treatment method using the diamond anvil device or the multiple anvil device shown in FIG. 3 or FIG. 4, it is preferable that the pressure range can be 12 GPa or more and 44 GPa before the treatment. The following range satisfies the range of 7.5 GPa to 40 GPa after the treatment. In the embodiment of the present invention, it is known that the pressure before heating (before processing) and the pressure after heating (after processing) can be quite different. By adjusting the pressures so that they respectively meet the above-mentioned ranges, it can be manufactured. The above-mentioned barium germanium oxide having a hexagonal 6H type perovskite structure. It is more preferable that the pressure range can be in a range of 12 GPa or more and 24 GPa or less before the treatment, and can satisfy a range of 8 GPa or more and 18.5 GPa or less after the treatment. The pressure before heating and the pressure after heating can be adjusted in such a manner that they satisfy the above ranges, respectively. In this way, the above-mentioned barium germanium oxide having a hexagonal 6H type perovskite structure can be manufactured in a single phase.

In the case where the above-mentioned treatment is performed by a high-temperature and high-pressure treatment method using a diamond anvil device or a multiple anvil device shown in FIG. 3 or FIG. 4, the temperature range may preferably be 1200 ° C. or higher and 2000 ° C. Temperature range. Within this range, the above-mentioned barium germanium oxide having a hexagonal 6H type perovskite structure can be manufactured. The temperature range is more preferably 1300 ° C to 1500 ° C. The pressure range may be in a range of 19.5 GPa to 24 GPa before the treatment. In addition, after the treatment, a range of 12.5 GPa or more and 16.5 GPa or less can be satisfied. You can choose this condition. In this way, the above-mentioned barium germanium oxide having a hexagonal 6H-type perovskite structure can be produced in a single phase with high yield.

Next, a case where processing is performed by a belt-type high-pressure device will be described. The belt-type high-pressure device uses a high-pressure unit including a capsule filled with raw material powder.

Fig. 5 is a schematic view showing a cross section of a high-pressure unit including a capsule for producing the barium germanium oxide of the present invention.

The high-pressure unit includes a cylindrical pyrophyllite 1, two steel rings arranged inside the barrel of the pyrophyllite 1 so as to be in contact with the upper and lower sides of the inner wall surface of the barrel, and 2 arranged on the central axis side of the steel ring 2. A cylindrical carbon heater 4, a metal capsule 8 arranged inside the carbon heater 4, and a raw material powder 7 filled inside the metal capsule 8. The gap between the pyrophyllite 1 and the carbon heater 4 is filled with a filling powder 3, and the gap between the carbon heater 4 and the metal capsule 8 is also filled with a filling powder 3. A metal electrode 6 such as Mo is disposed on the carbon heater 4. FIG. 5 shows a case where the metal capsule 8 is filled with a powder 7 of a normal pressure phase BaGeO ₃ .

After filling the inside of the cylindrical carbon heater 4 closed with a disc-shaped cover on one end side with the powder 5 for filling, a metal capsule 8 is arranged coaxially in the cylindrical carbon heater 4 , Filling the gap between the inner wall surface of the metal capsule 8 and the carbon heater 4 with the filling powder 3, and then filling the upper portion of the metal capsule 8 with the filling powder 5, and sealing the other end side with a disc-shaped cover .

After the cylindrical carbon heater 4 is disposed coaxially in the cylindrical pyrophyllite 1, the filling powder 3 is filled in the gap between the carbon heater 4 and the inner wall surface of the pyrophyllite 1. Examples of the filling powders 3 and 5 include NaCl + 10 wt% ZrO ₂ .

Next, the steel ring 2 is pressed into the filling powder 3 on the upper side of the inner wall surface of the pyrophyllite 1, and the other steel is pressed into the filling powder 3 on the lower side of the inner wall surface of the pyrophyllite 1. ring. As described above, a high-pressure unit in which the raw material powder 7 is filled in the metal capsule 8 can be obtained.

FIG. 6 is a view schematically showing a belt-type high-voltage device for producing the barium germanium oxide of the present invention.

At a specific position between the cylinders 27A and 27B of the belt-type high voltage device 21 and between the anvils 25A and 25B, the conductors 26A and 26B including the thin metal plate are contacted, and the high voltage unit described with reference to FIG. 5 is arranged . Second, pyrophyllite 28 is filled between the components and the high-voltage unit.

The anvils 25A and 25B and the cylinders 27A and 27B are moved to the high-pressure unit side, and the high-pressure unit is pressurized in such a manner as to satisfy the above-mentioned conditions. In a pressurized state, heating is performed in a manner that satisfies the above conditions, and it can be maintained for a specific time. For example, in the case of using the belt-type high-pressure device 21, if the processing is performed in a temperature range of 1100 ° C to 1300 ° C and a pressure range of 9 GPa to 10 GPa, the above-mentioned Barium germanium oxide with hexagonal 6H type perovskite structure.

So far, the barium germanium oxide of the present invention has been described as a solidified body or a powder obtained therefrom, but the barium germanium oxide of the present invention may be in the shape of a powder, a sintered body, or a thin film. For example, if the barium germanium oxide of the present invention in powder form obtained by the above method is formed and sintered, a sintered body can be obtained. Regarding the sintering, a hot pressing method, a cold equalizing pressure method (CIP), a hot equalizing pressure method (HIP), and a pulse current sintering method are used. If the sintered body thus obtained is used as a target in a physical vapor deposition method, the barium germanium oxide film of the present invention can be provided.

Next, the present invention is described in detail using specific embodiments, but it should be noted that the present invention is not limited to these embodiments.
[Example]

[Examples 1 to 18]
In Examples 1 to 18, barium germanium oxide (hereinafter referred to as orthorhombic BaGeO ₃ powder) represented by BaGeO ₃ having orthorhombic crystals was used as a raw material powder within the pressure range and temperature range shown in Table 2. The high temperature and high pressure treatment method using laser heating using the diamond anvil device shown in FIG. 3 and FIG. 4 was implemented.

First, an orthorhombic BaGeO ₃ powder as a raw material powder was synthesized as follows. GeO ₂ powder (manufactured by Aldrich, purity 99.99%) and BaCO ₃ (manufactured by Aldrich, purity 99.99%) were weighed so that the molar ratio became 1: 1, and mixed in a steel jade mortar. This mixed powder was pressed into granules (diameter: 10 mm, thickness: 5 mm). The pellets were placed in an electric furnace and calcined in the air at 1200 ° C for 8 hours. The calcined granules were pulverized in a steel jade mortar to make granules again, and calcined under the same conditions. Powder X-ray diffraction (XRD) was performed to identify the calcined body. The crystal structure parameters obtained from the XRD pattern were consistent with Pearson's Crystal Data # 1827134, and it was confirmed that the obtained calcined body was orthorhombic BaGeO ₃ .

As shown in FIG. 4, an orthorhombic BaGeO ₃ powder as a raw material powder is held by a pad and diamond. Here, the filled orthorhombic BaGeO ₃ powder has a particle diameter of about 100 μm, which is about 0.3 to 0.8 μg.

Next, as shown in Table 2, the pressure before the treatment (before heating) of the diamond anvil device was applied, and the laser beam was irradiated from the 100 W fiber laser to the raw material powder. Furthermore, the laser beam was condensed to 10 μmϕ, and the entire raw material powder was scanned and adjusted to the temperature range shown in Table 2. The heating temperature is determined by the color temperature. The laser irradiation time is several minutes (5 minutes to 10 minutes) after the temperature becomes constant. In addition, control was performed so that the pressure after the treatment (after heating) was the pressure shown in Table 2. In addition, when the pressure value is in the high pressure observation experiment of the DAC (Diamond Anvil Cell), the Raman scattering spectrum mixed with the diamond anvil and the X-ray diffraction of gold of the sample are used for measurement, and the DAC is recovered. In the case of the experiment, only the Raman scattering spectrum of the diamond anvil was used for the measurement, and the pressure of the latter was corrected based on the results of the pressure measurement of the former.

Fig. 7 is a diagram showing a measurement system for X-ray structure analysis.

As for the processed sample, as shown in FIG. 7, the diamond anvil unit is not directly decompressed, but is directly used in the measurement system unit for X-ray structural analysis. X-rays from the emitted light were monochromated with silicon (λ = 0.041476 nm, or 0.033242 nm, or 0.074996 nm) to obtain an X-ray diffraction pattern. X-ray structure analysis was performed from the obtained X-ray diffraction pattern, and crystal structure parameters such as a lattice constant were obtained. The results are shown in Table 3.

Next, for the processed sample, the diamond anvil unit was decompressed to an atmospheric pressure, the sample was taken out from the unit, and X-ray structure analysis was performed to obtain crystal structure parameters such as lattice constant. The results are shown in Fig. 8 and Table 3.

Furthermore, the diffuse reflection spectrum of the processed sample was measured using a diffuse reflection measuring device. The results are shown in FIG. 14.

[Example 19]
In Example 19, an orthorhombic BaGeO ₃ powder was used as a raw material powder, and the high-temperature and high-pressure treatment method using the belt-type high-pressure device shown in FIG. 5 and FIG. 6 was performed in the pressure range and temperature range shown in Table 2.

The orthorhombic BaGeO ₃ powder synthesized in Example 1 was filled into a cylindrical metal capsule (Au) made of Au (gold) closed at one end by a disc-shaped lid, and the other end The side is sealed with a disc-shaped lid made of Mo. At this time, the bulk density at the time of filling was 1.4 g / cm ³ . Next, the bottom of the cylindrical carbon heater (Fig. 5-4) closed with a disk-shaped cover on one end side is covered with filling powder (NaCl + 10 wt% ZrO ₂ ), and then the cylindrical carbon is heated. The metal capsule is arranged coaxially in the device, and the filling powder (NaCl + 10 wt% ZrO ₂ ) is filled in the gap between the metal capsule and the inner wall surface of the carbon heater, and the upper portion of the metal capsule is filled with a filling material. After powdering (NaCl + 10 wt% ZrO ₂ ), the other end side was sealed with a disc-shaped lid.

Next, the cylindrical carbon heater is arranged coaxially in the cylindrical pyrophyllite, and the filling powder (NaCl + 10 wt% ZrO ₂ ) is filled in the inner wall surface of the carbon heater and pyrophyllite. gap.

Next, a steel ring is pressed into the powder for filling on the upper side of the inner wall surface of pyrophyllite, and another steel ring is pressed into the powder for filling on the lower side of the inner wall surface of pyrophyllite. Proceed as above to make a high voltage unit.

The high-pressure unit is arranged at a specific position of the belt-type pressurizing device shown in FIG. 6. Pressurize the high-pressure unit to the pressure values shown in Table 2. Next, in a pressurized state, heating was performed at the temperature shown in Table 2. In this state, the temperature and pressure were maintained for 30 minutes. Thereby, the raw material powder is subjected to high-temperature and high-pressure treatment.

Return to room temperature and normal pressure, and take out the product inside the metal capsule. Next, the product was treated in water heated to 80 ° C. As a result, NaCl adhering to the product was dissolved and removed. Thus, a sample was obtained. X-ray structure analysis was performed on the obtained samples in the same manner as in Examples 1 to 18, and the diffuse reflection spectrum was measured. The results are shown in Table 3.

[Examples 20 to 21]
In Examples 20 to 21, orthorhombic BaGeO ₃ powder (the powder synthesized in Example 1), La ₂ O ₃ powder (manufactured by Aldrich, purity 99.99%), and GeO ₂ powder (manufactured by Aldrich, purity 99.999%) were used. As the raw material powder, a high-temperature and high-pressure treatment method using laser heating using a diamond anvil device shown in FIG. 3 and FIG. 4 was performed in the pressure range and temperature range shown in Table 2.

In detail, the orthorhombic BaGeO ₃ powder, La ₂ O ₃ powder, and GeO are mixed so that the amount of metal ions in the formula represented by Ba _1-x La _x GeO ₃ (x = 0.05, 0.10) is consistent. ₂ powder. As shown in Fig. 4, the mixed powder is held by a pad and diamond. Here, the weight of the mixed powder to be filled is about 0.3 to 0.8 μg. The following procedures are the same as those in Examples 1 to 18, and therefore descriptions are omitted.

For the treated sample, the diamond anvil unit was decompressed to an atmospheric pressure, the sample was taken out from the unit, and X-ray structure analysis was performed to obtain crystal structure parameters such as lattice constant. The results are shown in Fig. 8 and Table 3.

[Table 2]

The above results will be described with reference to Table 3 and FIGS. 8 to 14.

FIG. 8 is a diagram showing an XRD pattern of the sample (at one atmosphere) of Example 8. FIG.
Figure 9 is a diagram showing the XRD pattern of the sample (at one atmosphere) of Example 20.
Fig. 10 is a diagram showing the XRD pattern of the sample (at one atmosphere) of Example 21.

According to FIG. 8, the diffraction peaks can be indexed with a barium germanium oxide (6H type BaGeO ₃ ) having a perovskite structure exhibiting the symmetry of a hexagonal 6H type P6 ₃ / mmc space group. 9 and 10, the diffraction peaks can be indexed to the barium germanium oxide (6H type BaGeO ₃ ) having a perovskite structure that exhibits the symmetry of the hexagonal 6H type P6 ₃ / mmc space group. . In addition, no other peak showing the second phase was seen. Although not shown, the samples of Examples 2, 9, 11, 12, 14, 17 and 19 also showed the same XRD pattern.

In addition, the samples of Examples 1, 3, 5, 10, and 13 showed the same XRD pattern as in Example 8, and showed a wide halo pattern. From this, it can be seen that these samples contain 6H-type BaGeO ₃ and contain amorphous. In the sample of Example 6, a plurality of diffraction peaks were seen, part of which was indexed to 6H type BaGeO ₃ , and part of which was indexed to low-pressure type BaGeO ₃ . The samples of Examples 4, 7, 15, 16, and 18 did not show a peak corresponding to 6H-type BaGeO ₃ .

The above results are summarized in Table 3.

[table 3]

From these expressions, at least 6H-type BaGeO _{3 is} manufactured by using orthorhombic BaGeO ₃ powder as a raw material powder and processing in a temperature range of 900 ° C. to 2300 ° C. and a pressure range of 7.5 GPa to 45 GPa. .

11 is a graph showing the dependency of La addition amount per unit lattice length on the a-axis of the samples of Examples 8, 20, and 21;
FIG. 12 is a graph showing the dependence of La addition amount per unit lattice length on the c-axis of the samples of Examples 8, 20, and 21. FIG.
FIG. 13 is a graph showing the dependency of La addition amount per unit lattice volume on the samples of Examples 8, 20, and 21.

The results of Example 8 in which La is not added are shown in FIGS. 11 to 13. As can be seen from FIGS. 11 to 13, as the amount of La added increases, the lattice constants of the a-axis and the c-axis extend. As the amount of La added increases, the lattice volume increases. From this, it can be known that the added La is solid-dissolved in the Ba portion, and the addition amount thereof is more appropriate with an upper limit of 15 mol%.

In addition, it is shown that by adding, in addition to the orthorhombic BaGeO ₃ powder, a material selected from Y, Sc, In, Si, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, A substance of at least one element in the group consisting of Tm, Yb, and Lu is used as a raw material powder, and 6H-type BaGeO _{3 having a} part of Ba or a part of Ge substituted is produced. It is also shown that further addition of GeO ₂ is effective for adjusting the composition.

FIG. 14 is a graph showing a diffuse reflection spectrum of the sample of Example 8. FIG.

As shown in FIG. 14, the band gap (E _g ) obtained from the absorption end of the diffuse reflection spectrum was calculated to be 3.1 eV. Moreover, although not shown, the band gaps of the samples 2, 9, 11, 12, 14, 17, 19, 20, and 21, which are examples of the 6H-type BaGeO ₃ single phase, are all 2.5 eV or more and 3.5 eV or less. Within range.
[Industrial availability]

Since the barium germanium oxide of the present invention has a band gap of 4 eV or less, it can be made into a transparent conductive substance by dopant or defect control. In addition, if the barium germanium oxide of the present invention is used as a sintered body and used as a target, a thin film of barium germanium oxide can be provided, which can be applied to displays and the like.

1‧‧‧Pyrophyllite container (tube)

2‧‧‧ steel ring

3.5‧‧‧filling powder (NaCl + 10 wt% ZrO ₂ )

4‧‧‧carbon heater

6‧‧‧Mo electrode

7‧‧‧ raw material powder

8‧‧‧ metal capsules

21‧‧‧Belt type high voltage device

25A, 25B‧‧‧ Anvil

26A, 26B‧‧‧Conductor

27A, 27B‧‧‧ cylinder

28‧‧‧ Pyrophyllite (for filling)

a‧‧‧axis

b‧‧‧axis

c‧‧‧axis

FIG. 1 is a schematic view showing the crystal structure of the barium germanium oxide of the present invention.

FIG. 2 is a diagram illustrating a process of manufacturing the barium germanium oxide of the present invention.

FIG. 3 is a schematic view showing an entire diamond anvil device including a diamond anvil unit.

FIG. 4 is a schematic view showing details of the diamond anvil device of FIG. 3.

Fig. 5 is a schematic view showing a cross section of a high-pressure unit including a capsule for producing the barium germanium oxide of the present invention.

FIG. 6 is a view schematically showing a belt-type high-voltage device for producing the barium germanium oxide of the present invention.

Fig. 7 is a diagram showing a measurement system for X-ray structure analysis.

FIG. 8 is a diagram showing an XRD (X ray diffraction) pattern of the sample (at one atmospheric pressure) of Example 8. FIG.

Figure 9 is a diagram showing the XRD pattern of the sample (at one atmosphere) of Example 20.

Fig. 10 is a diagram showing the XRD pattern of the sample (at one atmosphere) of Example 21.

11 is a graph showing the dependency of La addition amount per unit lattice length on the a-axis of the samples of Examples 8, 20, and 21;

FIG. 12 is a graph showing the dependence of La addition amount per unit lattice length on the c-axis of the samples of Examples 8, 20, and 21. FIG.

FIG. 13 is a graph showing the dependency of La addition amount per unit lattice volume on the samples of Examples 8, 20, and 21.

FIG. 14 is a graph showing a diffuse reflection spectrum of the sample of Example 8. FIG.

Claims (18)

A barium germanium oxide contains a crystal represented by the general formula ABO ₃ (where A contains at least Ba and B contains at least Ge). The crystal represented by ABO ₃ has a hexagonal 6H type perovskite structure. For example, the barium germanium oxide of claim 1, in which the above-mentioned crystal represented by ABO ₃ has the symmetry of the space group P6 ₃ / mmc, and the lattice constants a, b, and c respectively satisfy the following ranges: a = 0.56006 ± 0.05 ( nm) b = 0.56006 ± 0.05 (nm) c = 1.3653 ± 0.1 (nm). The barium germanium oxide of claim 1 or 2 has a band gap in a range of 2.5 eV or more and 4 eV or less. The barium germanium oxide of claim 3 has a band gap in a range of 2.5 eV or more and 3.5 eV or less. For example, the barium germanium oxide of claim 1 or 2, wherein the A further contains a member selected from the group consisting of La (lanthanum), Ce (cerium), Pr (鐠), Nd (neodymium), Sm (钐), Eu (铕), and Gd. (釓), Tb (鋱), Dy (镝), Ho ('), Er (铒), Tm (銩), Yb (镱), Lu (镏), Y (yttrium), Sc (钪), and At least one element in the group consisting of In (indium). The barium germanium oxide according to claim 5, wherein the at least one element further contained as the A is in a range of 0.05 mol% or more and 15 mol% or less. The barium germanium oxide according to claim 1 or 2, wherein said B further contains Si. A method for manufacturing barium germanium oxide, comprising the steps of: 7.5 GPa of a raw material powder containing at least barium germanium oxide represented by BaGeO ₃ having an orthorhombic crystal at a temperature range of 900 ° C to 2300 ° C; It is processed in the pressure range above 45 GPa. The method of claim 8, wherein the above-mentioned processing step is performed by a high-temperature and high-pressure treatment method or impact using at least one device selected from the group consisting of a diamond anvil device, a multiple anvil device, and a belt-type high-voltage device. Compression method. As the method of claim 9, wherein the above-mentioned processing step is performed by a high-temperature and high-pressure processing method using a diamond anvil device or a multi-anvil device, the above-mentioned pressure range is in a range of 12 GPa or more and 44 GPa or less before processing. After treatment, the range is 7.5 GPa or more and 40 GPa or less. The method of claim 10, wherein the pressure range is in a range of 12 GPa or more and 24 GPa or less before processing, and 8.0 GPa or more and 18.5 GPa or less after processing. The method according to claim 11, wherein the temperature range is in a range of 1200 ° C or higher and 2000 ° C or lower. The method of claim 12, wherein the above temperature range is in the range of 1300 ° C to 1500 ° C, The above-mentioned pressure range is a range of 19.5 GPa or more and 24 GPa or less before the treatment, and a range of 12.5 GPa or more and 16.5 GPa or less after the treatment. The method according to any one of claims 8 to 13, wherein the raw material powder is a powder having a particle diameter of 100 nm or more and 500 μm or less. The method according to any one of claims 8 to 13, wherein the step of carrying out the treatment causes the raw material powder to react for a period of 5 minutes or more and 24 hours or less. The method according to any one of claims 8 to 13, wherein the raw material powder further contains a material selected from the group consisting of Y, Sc, In, Si, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, A substance of at least one element in the group consisting of Er, Tm, Yb, and Lu. A sintered body comprising a barium germanium oxide as claimed in claim 1 or 2. A target for physical vapor deposition, comprising the sintered body as claimed in claim 17.